Synthesis:
Epoxy resins or "epoxies" are solid or liquid linear polymers mainly obtained by the reaction of epichlorohydrin and bisphenol A (or diphenylolpropane).
The resulting resin has two highly reactive "epoxy" (or oxirane) sites at the chain ends and a number of less reactive "hydroxyl" groups in the middle of the chain.
Uses :
- High performance composite for aeronautics, sporting goods...
- Paints, glue, electrical and electronic insulation.
It is the resin offering the most interesting performance/price ratio.
Cross-linking of epoxies
The most used reaction is the one which involves the epoxy function with diamines which leads either to a linear condensation or to a three-dimensional cross-linking according to the epoxy ratio on active hydrogens.
This reaction occurs at ambient temperatures. The "pot life" is limited to a few hours at most, which makes it necessary to market the system in two separate components to be mixed at the time of application.
All amines, diamines, triamines, polyamines, aliphatic, cycloaliphatic, aromatic, primary or secondary, can be used depending on the performance required.
About epoxies
Generally speaking, epoxies are characterized by
- excellent adhesion to almost all substrates
- a very low shrinkage (almost zero) and therefore few internal tensions
- a very good resistance to hydrocarbons
- very good chemical resistance, especially to bases
- excellent dielectric properties, which naturally favors their use in electronics
- good mechanical properties
- Epoxies: Health, Safety and Environment
Epoxies: Health, Safety and Environment
Epoxy resins are generally classified as "Irritant" and "Dangerous for the environment". As for hardeners such as amines, they are classified as "Corrosive" and even "Toxic" for aromatic amines. However, the main risk encountered in handling epoxy resins is the allergy that causes acute dermatitis.
It is therefore necessary to wear adequate equipment (clothing, gloves and safety glasses) as well as to ensure good ventilation of the work stations.
Epoxy resins are only dangerous for the environment if they are spilled in nature. Indeed, epoxies do not contain VOCs (volatile organic compounds) and therefore do not pollute the atmosphere.
